/*
 * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */

package java.lang.invoke;

import java.lang.annotation.*;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Arrays;
import java.util.HashMap;

import sun.invoke.util.Wrapper;
import java.lang.reflect.Field;

import static java.lang.invoke.LambdaForm.BasicType.*;
import static java.lang.invoke.MethodHandleStatics.*;
import static java.lang.invoke.MethodHandleNatives.Constants.*;

/**
 * The symbolic, non-executable form of a method handle's invocation semantics. It consists of a
 * series of names. The first N (N=arity) names are parameters, while any remaining names are
 * temporary values. Each temporary specifies the application of a function to some arguments. The
 * functions are method handles, while the arguments are mixes of constant values and local names.
 * The result of the lambda is defined as one of the names, often the last one. <p> Here is an
 * approximate grammar:
 * <blockquote><pre>{@code
 * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"
 * ArgName = "a" N ":" T
 * TempName = "t" N ":" T "=" Function "(" Argument* ");"
 * Function = ConstantValue
 * Argument = NameRef | ConstantValue
 * Result = NameRef | "void"
 * NameRef = "a" N | "t" N
 * N = (any whole number)
 * T = "L" | "I" | "J" | "F" | "D" | "V"
 * }</pre></blockquote>
 * Names are numbered consecutively from left to right starting at zero. (The letters are merely a
 * taste of syntax sugar.) Thus, the first temporary (if any) is always numbered N (where N=arity).
 * Every occurrence of a name reference in an argument list must refer to a name previously defined
 * within the same lambda. A lambda has a void result if and only if its result index is -1. If a
 * temporary has the type "V", it cannot be the subject of a NameRef, even though possesses a
 * number. Note that all reference types are erased to "L", which stands for {@code Object}. All
 * subword types (boolean, byte, short, char) are erased to "I" which is {@code int}. The other
 * types stand for the usual primitive types. <p> Function invocation closely follows the static
 * rules of the Java verifier. Arguments and return values must exactly match when their "Name"
 * types are considered. Conversions are allowed only if they do not change the erased type. <ul>
 * <li>L = Object: casts are used freely to convert into and out of reference types <li>I = int:
 * subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})
 * <li>J = long: no implicit conversions <li>F = float: no implicit conversions <li>D = double: no
 * implicit conversions <li>V = void: a function result may be void if and only if its Name is of
 * type "V" </ul> Although implicit conversions are not allowed, explicit ones can easily be encoded
 * by using temporary expressions which call type-transformed identity functions. <p> Examples:
 * <blockquote><pre>{@code
 * (a0:J)=>{ a0 }
 *     == identity(long)
 * (a0:I)=>{ t1:V = System.out#println(a0); void }
 *     == System.out#println(int)
 * (a0:L)=>{ t1:V = System.out#println(a0); a0 }
 *     == identity, with printing side-effect
 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
 *                 t3:L = BoundMethodHandle#target(a0);
 *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }
 *     == general invoker for unary insertArgument combination
 * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);
 *                 t3:L = MethodHandle#invoke(t2, a1);
 *                 t4:L = FilterMethodHandle#target(a0);
 *                 t5:L = MethodHandle#invoke(t4, t3); t5 }
 *     == general invoker for unary filterArgument combination
 * (a0:L, a1:L)=>{ ...(same as previous example)...
 *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }
 *     == general invoker for unary/unary foldArgument combination
 * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }
 *     == invoker for identity method handle which performs i2l
 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
 *                 t3:L = Class#cast(t2,a1); t3 }
 *     == invoker for identity method handle which performs cast
 * }</pre></blockquote>
 * <p>
 *
 * @author John Rose, JSR 292 EG
 */
class LambdaForm {

  final int arity;
  final int result;
  final boolean forceInline;
  final MethodHandle customized;
  @Stable
  final Name[] names;
  final String debugName;
  MemberName vmentry;   // low-level behavior, or null if not yet prepared
  private boolean isCompiled;

  // Either a LambdaForm cache (managed by LambdaFormEditor) or a link to uncustomized version (for customized LF)
  volatile Object transformCache;

  public static final int VOID_RESULT = -1, LAST_RESULT = -2;

  enum BasicType {
    L_TYPE('L', Object.class, Wrapper.OBJECT),  // all reference types
    I_TYPE('I', int.class, Wrapper.INT),
    J_TYPE('J', long.class, Wrapper.LONG),
    F_TYPE('F', float.class, Wrapper.FLOAT),
    D_TYPE('D', double.class, Wrapper.DOUBLE),  // all primitive types
    V_TYPE('V', void.class, Wrapper.VOID);    // not valid in all contexts

    static final BasicType[] ALL_TYPES = BasicType.values();
    static final BasicType[] ARG_TYPES = Arrays.copyOf(ALL_TYPES, ALL_TYPES.length - 1);

    static final int ARG_TYPE_LIMIT = ARG_TYPES.length;
    static final int TYPE_LIMIT = ALL_TYPES.length;

    private final char btChar;
    private final Class<?> btClass;
    private final Wrapper btWrapper;

    private BasicType(char btChar, Class<?> btClass, Wrapper wrapper) {
      this.btChar = btChar;
      this.btClass = btClass;
      this.btWrapper = wrapper;
    }

    char basicTypeChar() {
      return btChar;
    }

    Class<?> basicTypeClass() {
      return btClass;
    }

    Wrapper basicTypeWrapper() {
      return btWrapper;
    }

    int basicTypeSlots() {
      return btWrapper.stackSlots();
    }

    static BasicType basicType(byte type) {
      return ALL_TYPES[type];
    }

    static BasicType basicType(char type) {
      switch (type) {
        case 'L':
          return L_TYPE;
        case 'I':
          return I_TYPE;
        case 'J':
          return J_TYPE;
        case 'F':
          return F_TYPE;
        case 'D':
          return D_TYPE;
        case 'V':
          return V_TYPE;
        // all subword types are represented as ints
        case 'Z':
        case 'B':
        case 'S':
        case 'C':
          return I_TYPE;
        default:
          throw newInternalError("Unknown type char: '" + type + "'");
      }
    }

    static BasicType basicType(Wrapper type) {
      char c = type.basicTypeChar();
      return basicType(c);
    }

    static BasicType basicType(Class<?> type) {
      if (!type.isPrimitive()) {
        return L_TYPE;
      }
      return basicType(Wrapper.forPrimitiveType(type));
    }

    static char basicTypeChar(Class<?> type) {
      return basicType(type).btChar;
    }

    static BasicType[] basicTypes(List<Class<?>> types) {
      BasicType[] btypes = new BasicType[types.size()];
      for (int i = 0; i < btypes.length; i++) {
        btypes[i] = basicType(types.get(i));
      }
      return btypes;
    }

    static BasicType[] basicTypes(String types) {
      BasicType[] btypes = new BasicType[types.length()];
      for (int i = 0; i < btypes.length; i++) {
        btypes[i] = basicType(types.charAt(i));
      }
      return btypes;
    }

    static byte[] basicTypesOrd(BasicType[] btypes) {
      byte[] ords = new byte[btypes.length];
      for (int i = 0; i < btypes.length; i++) {
        ords[i] = (byte) btypes[i].ordinal();
      }
      return ords;
    }

    static boolean isBasicTypeChar(char c) {
      return "LIJFDV".indexOf(c) >= 0;
    }

    static boolean isArgBasicTypeChar(char c) {
      return "LIJFD".indexOf(c) >= 0;
    }

    static {
      assert (checkBasicType());
    }

    private static boolean checkBasicType() {
      for (int i = 0; i < ARG_TYPE_LIMIT; i++) {
        assert ARG_TYPES[i].ordinal() == i;
        assert ARG_TYPES[i] == ALL_TYPES[i];
      }
      for (int i = 0; i < TYPE_LIMIT; i++) {
        assert ALL_TYPES[i].ordinal() == i;
      }
      assert ALL_TYPES[TYPE_LIMIT - 1] == V_TYPE;
      assert !Arrays.asList(ARG_TYPES).contains(V_TYPE);
      return true;
    }
  }

  LambdaForm(String debugName,
      int arity, Name[] names, int result) {
    this(debugName, arity, names, result, /*forceInline=*/true, /*customized=*/null);
  }

  LambdaForm(String debugName,
      int arity, Name[] names, int result, boolean forceInline, MethodHandle customized) {
    assert (namesOK(arity, names));
    this.arity = arity;
    this.result = fixResult(result, names);
    this.names = names.clone();
    this.debugName = fixDebugName(debugName);
    this.forceInline = forceInline;
    this.customized = customized;
    int maxOutArity = normalize();
    if (maxOutArity > MethodType.MAX_MH_INVOKER_ARITY) {
      // Cannot use LF interpreter on very high arity expressions.
      assert (maxOutArity <= MethodType.MAX_JVM_ARITY);
      compileToBytecode();
    }
  }

  LambdaForm(String debugName,
      int arity, Name[] names) {
    this(debugName, arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null);
  }

  LambdaForm(String debugName,
      int arity, Name[] names, boolean forceInline) {
    this(debugName, arity, names, LAST_RESULT, forceInline, /*customized=*/null);
  }

  LambdaForm(String debugName,
      Name[] formals, Name[] temps, Name result) {
    this(debugName,
        formals.length, buildNames(formals, temps, result), LAST_RESULT, /*forceInline=*/true, /*customized=*/
        null);
  }

  LambdaForm(String debugName,
      Name[] formals, Name[] temps, Name result, boolean forceInline) {
    this(debugName,
        formals.length, buildNames(formals, temps, result), LAST_RESULT, forceInline, /*customized=*/
        null);
  }

  private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {
    int arity = formals.length;
    int length = arity + temps.length + (result == null ? 0 : 1);
    Name[] names = Arrays.copyOf(formals, length);
    System.arraycopy(temps, 0, names, arity, temps.length);
    if (result != null) {
      names[length - 1] = result;
    }
    return names;
  }

  private LambdaForm(String sig) {
    // Make a blank lambda form, which returns a constant zero or null.
    // It is used as a template for managing the invocation of similar forms that are non-empty.
    // Called only from getPreparedForm.
    assert (isValidSignature(sig));
    this.arity = signatureArity(sig);
    this.result = (signatureReturn(sig) == V_TYPE ? -1 : arity);
    this.names = buildEmptyNames(arity, sig);
    this.debugName = "LF.zero";
    this.forceInline = true;
    this.customized = null;
    assert (nameRefsAreLegal());
    assert (isEmpty());
    assert (sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();
  }

  private static Name[] buildEmptyNames(int arity, String basicTypeSignature) {
    assert (isValidSignature(basicTypeSignature));
    int resultPos = arity + 1;  // skip '_'
    if (arity < 0 || basicTypeSignature.length() != resultPos + 1) {
      throw new IllegalArgumentException("bad arity for " + basicTypeSignature);
    }
    int numRes = (basicType(basicTypeSignature.charAt(resultPos)) == V_TYPE ? 0 : 1);
    Name[] names = arguments(numRes, basicTypeSignature.substring(0, arity));
    for (int i = 0; i < numRes; i++) {
      Name zero = new Name(constantZero(basicType(basicTypeSignature.charAt(resultPos + i))));
      names[arity + i] = zero.newIndex(arity + i);
    }
    return names;
  }

  private static int fixResult(int result, Name[] names) {
    if (result == LAST_RESULT) {
      result = names.length - 1;  // might still be void
    }
    if (result >= 0 && names[result].type == V_TYPE) {
      result = VOID_RESULT;
    }
    return result;
  }

  private static String fixDebugName(String debugName) {
    if (DEBUG_NAME_COUNTERS != null) {
      int under = debugName.indexOf('_');
      int length = debugName.length();
      if (under < 0) {
        under = length;
      }
      String debugNameStem = debugName.substring(0, under);
      Integer ctr;
      synchronized (DEBUG_NAME_COUNTERS) {
        ctr = DEBUG_NAME_COUNTERS.get(debugNameStem);
        if (ctr == null) {
          ctr = 0;
        }
        DEBUG_NAME_COUNTERS.put(debugNameStem, ctr + 1);
      }
      StringBuilder buf = new StringBuilder(debugNameStem);
      buf.append('_');
      int leadingZero = buf.length();
      buf.append((int) ctr);
      for (int i = buf.length() - leadingZero; i < 3; i++) {
        buf.insert(leadingZero, '0');
      }
      if (under < length) {
        ++under;    // skip "_"
        while (under < length && Character.isDigit(debugName.charAt(under))) {
          ++under;
        }
        if (under < length && debugName.charAt(under) == '_') {
          ++under;
        }
        if (under < length) {
          buf.append('_').append(debugName, under, length);
        }
      }
      return buf.toString();
    }
    return debugName;
  }

  private static boolean namesOK(int arity, Name[] names) {
    for (int i = 0; i < names.length; i++) {
      Name n = names[i];
      assert (n != null) : "n is null";
      if (i < arity) {
        assert (n.isParam()) : n + " is not param at " + i;
      } else {
        assert (!n.isParam()) : n + " is param at " + i;
      }
    }
    return true;
  }

  /**
   * Customize LambdaForm for a particular MethodHandle
   */
  LambdaForm customize(MethodHandle mh) {
    LambdaForm customForm = new LambdaForm(debugName, arity, names, result, forceInline, mh);
    if (COMPILE_THRESHOLD > 0 && isCompiled) {
      // If shared LambdaForm has been compiled, compile customized version as well.
      customForm.compileToBytecode();
    }
    customForm.transformCache = this; // LambdaFormEditor should always use uncustomized form.
    return customForm;
  }

  /**
   * Get uncustomized flavor of the LambdaForm
   */
  LambdaForm uncustomize() {
    if (customized == null) {
      return this;
    }
    assert (transformCache
        != null); // Customized LambdaForm should always has a link to uncustomized version.
    LambdaForm uncustomizedForm = (LambdaForm) transformCache;
    if (COMPILE_THRESHOLD > 0 && isCompiled) {
      // If customized LambdaForm has been compiled, compile uncustomized version as well.
      uncustomizedForm.compileToBytecode();
    }
    return uncustomizedForm;
  }

  /**
   * Renumber and/or replace params so that they are interned and canonically numbered.
   *
   * @return maximum argument list length among the names (since we have to pass over them anyway)
   */
  private int normalize() {
    Name[] oldNames = null;
    int maxOutArity = 0;
    int changesStart = 0;
    for (int i = 0; i < names.length; i++) {
      Name n = names[i];
      if (!n.initIndex(i)) {
        if (oldNames == null) {
          oldNames = names.clone();
          changesStart = i;
        }
        names[i] = n.cloneWithIndex(i);
      }
      if (n.arguments != null && maxOutArity < n.arguments.length) {
        maxOutArity = n.arguments.length;
      }
    }
    if (oldNames != null) {
      int startFixing = arity;
      if (startFixing <= changesStart) {
        startFixing = changesStart + 1;
      }
      for (int i = startFixing; i < names.length; i++) {
        Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);
        names[i] = fixed.newIndex(i);
      }
    }
    assert (nameRefsAreLegal());
    int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);
    boolean needIntern = false;
    for (int i = 0; i < maxInterned; i++) {
      Name n = names[i], n2 = internArgument(n);
      if (n != n2) {
        names[i] = n2;
        needIntern = true;
      }
    }
    if (needIntern) {
      for (int i = arity; i < names.length; i++) {
        names[i].internArguments();
      }
    }
    assert (nameRefsAreLegal());
    return maxOutArity;
  }

  /**
   * Check that all embedded Name references are localizable to this lambda,
   * and are properly ordered after their corresponding definitions.
   * <p>
   * Note that a Name can be local to multiple lambdas, as long as
   * it possesses the same index in each use site.
   * This allows Name references to be freely reused to construct
   * fresh lambdas, without confusion.
   */
  boolean nameRefsAreLegal() {
    assert (arity >= 0 && arity <= names.length);
    assert (result >= -1 && result < names.length);
    // Do all names possess an index consistent with their local definition order?
    for (int i = 0; i < arity; i++) {
      Name n = names[i];
      assert (n.index() == i) : Arrays.asList(n.index(), i);
      assert (n.isParam());
    }
    // Also, do all local name references
    for (int i = arity; i < names.length; i++) {
      Name n = names[i];
      assert (n.index() == i);
      for (Object arg : n.arguments) {
        if (arg instanceof Name) {
          Name n2 = (Name) arg;
          int i2 = n2.index;
          assert (0 <= i2 && i2 < names.length) :
              n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;
          assert (names[i2] == n2) : Arrays
              .asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-",
                  names[i2].debugString(), "-6-", this);
          assert (i2 < i);  // ref must come after def!
        }
      }
    }
    return true;
  }

  /** Invoke this form on the given arguments. */
  // final Object invoke(Object... args) throws Throwable {
  //     // NYI: fit this into the fast path?
  //     return interpretWithArguments(args);
  // }

  /**
   * Report the return type.
   */
  BasicType returnType() {
    if (result < 0) {
      return V_TYPE;
    }
    Name n = names[result];
    return n.type;
  }

  /**
   * Report the N-th argument type.
   */
  BasicType parameterType(int n) {
    return parameter(n).type;
  }

  /**
   * Report the N-th argument name.
   */
  Name parameter(int n) {
    assert (n < arity);
    Name param = names[n];
    assert (param.isParam());
    return param;
  }

  /**
   * Report the N-th argument type constraint.
   */
  Object parameterConstraint(int n) {
    return parameter(n).constraint;
  }

  /**
   * Report the arity.
   */
  int arity() {
    return arity;
  }

  /**
   * Report the number of expressions (non-parameter names).
   */
  int expressionCount() {
    return names.length - arity;
  }

  /**
   * Return the method type corresponding to my basic type signature.
   */
  MethodType methodType() {
    return signatureType(basicTypeSignature());
  }

  /**
   * Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character.
   */
  final String basicTypeSignature() {
    StringBuilder buf = new StringBuilder(arity() + 3);
    for (int i = 0, a = arity(); i < a; i++) {
      buf.append(parameterType(i).basicTypeChar());
    }
    return buf.append('_').append(returnType().basicTypeChar()).toString();
  }

  static int signatureArity(String sig) {
    assert (isValidSignature(sig));
    return sig.indexOf('_');
  }

  static BasicType signatureReturn(String sig) {
    return basicType(sig.charAt(signatureArity(sig) + 1));
  }

  static boolean isValidSignature(String sig) {
    int arity = sig.indexOf('_');
    if (arity < 0) {
      return false;  // must be of the form *_*
    }
    int siglen = sig.length();
    if (siglen != arity + 2) {
      return false;  // *_X
    }
    for (int i = 0; i < siglen; i++) {
      if (i == arity) {
        continue;  // skip '_'
      }
      char c = sig.charAt(i);
      if (c == 'V') {
        return (i == siglen - 1 && arity == siglen - 2);
      }
      if (!isArgBasicTypeChar(c)) {
        return false; // must be [LIJFD]
      }
    }
    return true;  // [LIJFD]*_[LIJFDV]
  }

  static MethodType signatureType(String sig) {
    Class<?>[] ptypes = new Class<?>[signatureArity(sig)];
    for (int i = 0; i < ptypes.length; i++) {
      ptypes[i] = basicType(sig.charAt(i)).btClass;
    }
    Class<?> rtype = signatureReturn(sig).btClass;
    return MethodType.methodType(rtype, ptypes);
  }

    /*
     * Code generation issues:
     *
     * Compiled LFs should be reusable in general.
     * The biggest issue is how to decide when to pull a name into
     * the bytecode, versus loading a reified form from the MH data.
     *
     * For example, an asType wrapper may require execution of a cast
     * after a call to a MH.  The target type of the cast can be placed
     * as a constant in the LF itself.  This will force the cast type
     * to be compiled into the bytecodes and native code for the MH.
     * Or, the target type of the cast can be erased in the LF, and
     * loaded from the MH data.  (Later on, if the MH as a whole is
     * inlined, the data will flow into the inlined instance of the LF,
     * as a constant, and the end result will be an optimal cast.)
     *
     * This erasure of cast types can be done with any use of
     * reference types.  It can also be done with whole method
     * handles.  Erasing a method handle might leave behind
     * LF code that executes correctly for any MH of a given
     * type, and load the required MH from the enclosing MH's data.
     * Or, the erasure might even erase the expected MT.
     *
     * Also, for direct MHs, the MemberName of the target
     * could be erased, and loaded from the containing direct MH.
     * As a simple case, a LF for all int-valued non-static
     * field getters would perform a cast on its input argument
     * (to non-constant base type derived from the MemberName)
     * and load an integer value from the input object
     * (at a non-constant offset also derived from the MemberName).
     * Such MN-erased LFs would be inlinable back to optimized
     * code, whenever a constant enclosing DMH is available
     * to supply a constant MN from its data.
     *
     * The main problem here is to keep LFs reasonably generic,
     * while ensuring that hot spots will inline good instances.
     * "Reasonably generic" means that we don't end up with
     * repeated versions of bytecode or machine code that do
     * not differ in their optimized form.  Repeated versions
     * of machine would have the undesirable overheads of
     * (a) redundant compilation work and (b) extra I$ pressure.
     * To control repeated versions, we need to be ready to
     * erase details from LFs and move them into MH data,
     * whevener those details are not relevant to significant
     * optimization.  "Significant" means optimization of
     * code that is actually hot.
     *
     * Achieving this may require dynamic splitting of MHs, by replacing
     * a generic LF with a more specialized one, on the same MH,
     * if (a) the MH is frequently executed and (b) the MH cannot
     * be inlined into a containing caller, such as an invokedynamic.
     *
     * Compiled LFs that are no longer used should be GC-able.
     * If they contain non-BCP references, they should be properly
     * interlinked with the class loader(s) that their embedded types
     * depend on.  This probably means that reusable compiled LFs
     * will be tabulated (indexed) on relevant class loaders,
     * or else that the tables that cache them will have weak links.
     */

  /**
   * Make this LF directly executable, as part of a MethodHandle.
   * Invariant:  Every MH which is invoked must prepare its LF
   * before invocation.
   * (In principle, the JVM could do this very lazily,
   * as a sort of pre-invocation linkage step.)
   */
  public void prepare() {
    if (COMPILE_THRESHOLD == 0 && !isCompiled) {
      compileToBytecode();
    }
    if (this.vmentry != null) {
      // already prepared (e.g., a primitive DMH invoker form)
      return;
    }
    LambdaForm prep = getPreparedForm(basicTypeSignature());
    this.vmentry = prep.vmentry;
    // TO DO: Maybe add invokeGeneric, invokeWithArguments
  }

  /**
   * Generate optimizable bytecode for this form.
   */
  MemberName compileToBytecode() {
    if (vmentry != null && isCompiled) {
      return vmentry;  // already compiled somehow
    }
    MethodType invokerType = methodType();
    assert (vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));
    try {
      vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);
      if (TRACE_INTERPRETER) {
        traceInterpreter("compileToBytecode", this);
      }
      isCompiled = true;
      return vmentry;
    } catch (Error | Exception ex) {
      throw newInternalError(this.toString(), ex);
    }
  }

  private static void computeInitialPreparedForms() {
    // Find all predefined invokers and associate them with canonical empty lambda forms.
    for (MemberName m : MemberName.getFactory()
        .getMethods(LambdaForm.class, false, null, null, null)) {
      if (!m.isStatic() || !m.isPackage()) {
        continue;
      }
      MethodType mt = m.getMethodType();
      if (mt.parameterCount() > 0 &&
          mt.parameterType(0) == MethodHandle.class &&
          m.getName().startsWith("interpret_")) {
        String sig = basicTypeSignature(mt);
        assert (m.getName().equals("interpret" + sig.substring(sig.indexOf('_'))));
        LambdaForm form = new LambdaForm(sig);
        form.vmentry = m;
        form = mt.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, form);
      }
    }
  }

  // Set this false to disable use of the interpret_L methods defined in this file.
  private static final boolean USE_PREDEFINED_INTERPRET_METHODS = true;

  // The following are predefined exact invokers.  The system must build
  // a separate invoker for each distinct signature.
  static Object interpret_L(MethodHandle mh) throws Throwable {
    Object[] av = {mh};
    String sig = null;
    assert (argumentTypesMatch(sig = "L_L", av));
    Object res = mh.form.interpretWithArguments(av);
    assert (returnTypesMatch(sig, av, res));
    return res;
  }

  static Object interpret_L(MethodHandle mh, Object x1) throws Throwable {
    Object[] av = {mh, x1};
    String sig = null;
    assert (argumentTypesMatch(sig = "LL_L", av));
    Object res = mh.form.interpretWithArguments(av);
    assert (returnTypesMatch(sig, av, res));
    return res;
  }

  static Object interpret_L(MethodHandle mh, Object x1, Object x2) throws Throwable {
    Object[] av = {mh, x1, x2};
    String sig = null;
    assert (argumentTypesMatch(sig = "LLL_L", av));
    Object res = mh.form.interpretWithArguments(av);
    assert (returnTypesMatch(sig, av, res));
    return res;
  }

  private static LambdaForm getPreparedForm(String sig) {
    MethodType mtype = signatureType(sig);
    LambdaForm prep = mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);
    if (prep != null) {
      return prep;
    }
    assert (isValidSignature(sig));
    prep = new LambdaForm(sig);
    prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(sig);
    return mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);
  }

  // The next few routines are called only from assert expressions
  // They verify that the built-in invokers process the correct raw data types.
  private static boolean argumentTypesMatch(String sig, Object[] av) {
    int arity = signatureArity(sig);
    assert (av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;
    assert (av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];
    MethodHandle mh = (MethodHandle) av[0];
    MethodType mt = mh.type();
    assert (mt.parameterCount() == arity - 1);
    for (int i = 0; i < av.length; i++) {
      Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i - 1));
      assert (valueMatches(basicType(sig.charAt(i)), pt, av[i]));
    }
    return true;
  }

  private static boolean valueMatches(BasicType tc, Class<?> type, Object x) {
    // The following line is needed because (...)void method handles can use non-void invokers
    if (type == void.class) {
      tc = V_TYPE;   // can drop any kind of value
    }
    assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);
    switch (tc) {
      case I_TYPE:
        assert checkInt(type, x) : "checkInt(" + type + "," + x + ")";
        break;
      case J_TYPE:
        assert x instanceof Long : "instanceof Long: " + x;
        break;
      case F_TYPE:
        assert x instanceof Float : "instanceof Float: " + x;
        break;
      case D_TYPE:
        assert x instanceof Double : "instanceof Double: " + x;
        break;
      case L_TYPE:
        assert checkRef(type, x) : "checkRef(" + type + "," + x + ")";
        break;
      case V_TYPE:
        break;  // allow anything here; will be dropped
      default:
        assert (false);
    }
    return true;
  }

  private static boolean returnTypesMatch(String sig, Object[] av, Object res) {
    MethodHandle mh = (MethodHandle) av[0];
    return valueMatches(signatureReturn(sig), mh.type().returnType(), res);
  }

  private static boolean checkInt(Class<?> type, Object x) {
    assert (x instanceof Integer);
    if (type == int.class) {
      return true;
    }
    Wrapper w = Wrapper.forBasicType(type);
    assert (w.isSubwordOrInt());
    Object x1 = Wrapper.INT.wrap(w.wrap(x));
    return x.equals(x1);
  }

  private static boolean checkRef(Class<?> type, Object x) {
    assert (!type.isPrimitive());
    if (x == null) {
      return true;
    }
    if (type.isInterface()) {
      return true;
    }
    return type.isInstance(x);
  }

  /**
   * If the invocation count hits the threshold we spin bytecodes and call that subsequently.
   */
  private static final int COMPILE_THRESHOLD;

  static {
    COMPILE_THRESHOLD = Math.max(-1, MethodHandleStatics.COMPILE_THRESHOLD);
  }

  private int invocationCounter = 0;

  @Hidden
  @DontInline
  /** Interpretively invoke this form on the given arguments. */
  Object interpretWithArguments(Object... argumentValues) throws Throwable {
    if (TRACE_INTERPRETER) {
      return interpretWithArgumentsTracing(argumentValues);
    }
    checkInvocationCounter();
    assert (arityCheck(argumentValues));
    Object[] values = Arrays.copyOf(argumentValues, names.length);
    for (int i = argumentValues.length; i < values.length; i++) {
      values[i] = interpretName(names[i], values);
    }
    Object rv = (result < 0) ? null : values[result];
    assert (resultCheck(argumentValues, rv));
    return rv;
  }

  @Hidden
  @DontInline
  /** Evaluate a single Name within this form, applying its function to its arguments. */
  Object interpretName(Name name, Object[] values) throws Throwable {
    if (TRACE_INTERPRETER) {
      traceInterpreter("| interpretName", name.debugString(), (Object[]) null);
    }
    Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);
    for (int i = 0; i < arguments.length; i++) {
      Object a = arguments[i];
      if (a instanceof Name) {
        int i2 = ((Name) a).index();
        assert (names[i2] == a);
        a = values[i2];
        arguments[i] = a;
      }
    }
    return name.function.invokeWithArguments(arguments);
  }

  private void checkInvocationCounter() {
    if (COMPILE_THRESHOLD != 0 &&
        invocationCounter < COMPILE_THRESHOLD) {
      invocationCounter++;  // benign race
      if (invocationCounter >= COMPILE_THRESHOLD) {
        // Replace vmentry with a bytecode version of this LF.
        compileToBytecode();
      }
    }
  }

  Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {
    traceInterpreter("[ interpretWithArguments", this, argumentValues);
    if (invocationCounter < COMPILE_THRESHOLD) {
      int ctr = invocationCounter++;  // benign race
      traceInterpreter("| invocationCounter", ctr);
      if (invocationCounter >= COMPILE_THRESHOLD) {
        compileToBytecode();
      }
    }
    Object rval;
    try {
      assert (arityCheck(argumentValues));
      Object[] values = Arrays.copyOf(argumentValues, names.length);
      for (int i = argumentValues.length; i < values.length; i++) {
        values[i] = interpretName(names[i], values);
      }
      rval = (result < 0) ? null : values[result];
    } catch (Throwable ex) {
      traceInterpreter("] throw =>", ex);
      throw ex;
    }
    traceInterpreter("] return =>", rval);
    return rval;
  }

  static void traceInterpreter(String event, Object obj, Object... args) {
    if (TRACE_INTERPRETER) {
      System.out.println(
          "LFI: " + event + " " + (obj != null ? obj : "") + (args != null && args.length != 0
              ? Arrays.asList(args) : ""));
    }
  }

  static void traceInterpreter(String event, Object obj) {
    traceInterpreter(event, obj, (Object[]) null);
  }

  private boolean arityCheck(Object[] argumentValues) {
    assert (argumentValues.length == arity) :
        arity + "!=" + Arrays.asList(argumentValues) + ".length";
    // also check that the leading (receiver) argument is somehow bound to this LF:
    assert (argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];
    MethodHandle mh = (MethodHandle) argumentValues[0];
    assert (mh.internalForm() == this);
    // note:  argument #0 could also be an interface wrapper, in the future
    argumentTypesMatch(basicTypeSignature(), argumentValues);
    return true;
  }

  private boolean resultCheck(Object[] argumentValues, Object result) {
    MethodHandle mh = (MethodHandle) argumentValues[0];
    MethodType mt = mh.type();
    assert (valueMatches(returnType(), mt.returnType(), result));
    return true;
  }

  private boolean isEmpty() {
    if (result < 0) {
      return (names.length == arity);
    } else if (result == arity && names.length == arity + 1) {
      return names[arity].isConstantZero();
    } else {
      return false;
    }
  }

  public String toString() {
    StringBuilder buf = new StringBuilder(debugName + "=Lambda(");
    for (int i = 0; i < names.length; i++) {
      if (i == arity) {
        buf.append(")=>{");
      }
      Name n = names[i];
      if (i >= arity) {
        buf.append("\n    ");
      }
      buf.append(n.paramString());
      if (i < arity) {
        if (i + 1 < arity) {
          buf.append(",");
        }
        continue;
      }
      buf.append("=").append(n.exprString());
      buf.append(";");
    }
    if (arity == names.length) {
      buf.append(")=>{");
    }
    buf.append(result < 0 ? "void" : names[result]).append("}");
    if (TRACE_INTERPRETER) {
      // Extra verbosity:
      buf.append(":").append(basicTypeSignature());
      buf.append("/").append(vmentry);
    }
    return buf.toString();
  }

  @Override
  public boolean equals(Object obj) {
    return obj instanceof LambdaForm && equals((LambdaForm) obj);
  }

  public boolean equals(LambdaForm that) {
    if (this.result != that.result) {
      return false;
    }
    return Arrays.equals(this.names, that.names);
  }

  public int hashCode() {
    return result + 31 * Arrays.hashCode(names);
  }

  LambdaFormEditor editor() {
    return LambdaFormEditor.lambdaFormEditor(this);
  }

  boolean contains(Name name) {
    int pos = name.index();
    if (pos >= 0) {
      return pos < names.length && name.equals(names[pos]);
    }
    for (int i = arity; i < names.length; i++) {
      if (name.equals(names[i])) {
        return true;
      }
    }
    return false;
  }

  LambdaForm addArguments(int pos, BasicType... types) {
    // names array has MH in slot 0; skip it.
    int argpos = pos + 1;
    assert (argpos <= arity);
    int length = names.length;
    int inTypes = types.length;
    Name[] names2 = Arrays.copyOf(names, length + inTypes);
    int arity2 = arity + inTypes;
    int result2 = result;
    if (result2 >= argpos) {
      result2 += inTypes;
    }
    // Note:  The LF constructor will rename names2[argpos...].
    // Make space for new arguments (shift temporaries).
    System.arraycopy(names, argpos, names2, argpos + inTypes, length - argpos);
    for (int i = 0; i < inTypes; i++) {
      names2[argpos + i] = new Name(types[i]);
    }
    return new LambdaForm(debugName, arity2, names2, result2);
  }

  LambdaForm addArguments(int pos, List<Class<?>> types) {
    return addArguments(pos, basicTypes(types));
  }

  LambdaForm permuteArguments(int skip, int[] reorder, BasicType[] types) {
    // Note:  When inArg = reorder[outArg], outArg is fed by a copy of inArg.
    // The types are the types of the new (incoming) arguments.
    int length = names.length;
    int inTypes = types.length;
    int outArgs = reorder.length;
    assert (skip + outArgs == arity);
    assert (permutedTypesMatch(reorder, types, names, skip));
    int pos = 0;
    // skip trivial first part of reordering:
    while (pos < outArgs && reorder[pos] == pos) {
      pos += 1;
    }
    Name[] names2 = new Name[length - outArgs + inTypes];
    System.arraycopy(names, 0, names2, 0, skip + pos);
    // copy the body:
    int bodyLength = length - arity;
    System.arraycopy(names, skip + outArgs, names2, skip + inTypes, bodyLength);
    int arity2 = names2.length - bodyLength;
    int result2 = result;
    if (result2 >= 0) {
      if (result2 < skip + outArgs) {
        // return the corresponding inArg
        result2 = reorder[result2 - skip];
      } else {
        result2 = result2 - outArgs + inTypes;
      }
    }
    // rework names in the body:
    for (int j = pos; j < outArgs; j++) {
      Name n = names[skip + j];
      int i = reorder[j];
      // replace names[skip+j] by names2[skip+i]
      Name n2 = names2[skip + i];
      if (n2 == null) {
        names2[skip + i] = n2 = new Name(types[i]);
      } else {
        assert (n2.type == types[i]);
      }
      for (int k = arity2; k < names2.length; k++) {
        names2[k] = names2[k].replaceName(n, n2);
      }
    }
    // some names are unused, but must be filled in
    for (int i = skip + pos; i < arity2; i++) {
      if (names2[i] == null) {
        names2[i] = argument(i, types[i - skip]);
      }
    }
    for (int j = arity; j < names.length; j++) {
      int i = j - arity + arity2;
      // replace names2[i] by names[j]
      Name n = names[j];
      Name n2 = names2[i];
      if (n != n2) {
        for (int k = i + 1; k < names2.length; k++) {
          names2[k] = names2[k].replaceName(n, n2);
        }
      }
    }
    return new LambdaForm(debugName, arity2, names2, result2);
  }

  static boolean permutedTypesMatch(int[] reorder, BasicType[] types, Name[] names, int skip) {
    int inTypes = types.length;
    int outArgs = reorder.length;
    for (int i = 0; i < outArgs; i++) {
      assert (names[skip + i].isParam());
      assert (names[skip + i].type == types[reorder[i]]);
    }
    return true;
  }

  static class NamedFunction {

    final MemberName member;
    @Stable
    MethodHandle resolvedHandle;
    @Stable
    MethodHandle invoker;

    NamedFunction(MethodHandle resolvedHandle) {
      this(resolvedHandle.internalMemberName(), resolvedHandle);
    }

    NamedFunction(MemberName member, MethodHandle resolvedHandle) {
      this.member = member;
      this.resolvedHandle = resolvedHandle;
      // The following assert is almost always correct, but will fail for corner cases, such as PrivateInvokeTest.
      //assert(!isInvokeBasic());
    }

    NamedFunction(MethodType basicInvokerType) {
      assert (basicInvokerType == basicInvokerType.basicType()) : basicInvokerType;
      if (basicInvokerType.parameterSlotCount() < MethodType.MAX_MH_INVOKER_ARITY) {
        this.resolvedHandle = basicInvokerType.invokers().basicInvoker();
        this.member = resolvedHandle.internalMemberName();
      } else {
        // necessary to pass BigArityTest
        this.member = Invokers.invokeBasicMethod(basicInvokerType);
      }
      assert (isInvokeBasic());
    }

    private boolean isInvokeBasic() {
      return member != null &&
          member.isMethodHandleInvoke() &&
          "invokeBasic".equals(member.getName());
    }

    // The next 3 constructors are used to break circular dependencies on MH.invokeStatic, etc.
    // Any LambdaForm containing such a member is not interpretable.
    // This is OK, since all such LFs are prepared with special primitive vmentry points.
    // And even without the resolvedHandle, the name can still be compiled and optimized.
    NamedFunction(Method method) {
      this(new MemberName(method));
    }

    NamedFunction(Field field) {
      this(new MemberName(field));
    }

    NamedFunction(MemberName member) {
      this.member = member;
      this.resolvedHandle = null;
    }

    MethodHandle resolvedHandle() {
      if (resolvedHandle == null) {
        resolve();
      }
      return resolvedHandle;
    }

    void resolve() {
      resolvedHandle = DirectMethodHandle.make(member);
    }

    @Override
    public boolean equals(Object other) {
      if (this == other) {
        return true;
      }
      if (other == null) {
        return false;
      }
      if (!(other instanceof NamedFunction)) {
        return false;
      }
      NamedFunction that = (NamedFunction) other;
      return this.member != null && this.member.equals(that.member);
    }

    @Override
    public int hashCode() {
      if (member != null) {
        return member.hashCode();
      }
      return super.hashCode();
    }

    // Put the predefined NamedFunction invokers into the table.
    static void initializeInvokers() {
      for (MemberName m : MemberName.getFactory()
          .getMethods(NamedFunction.class, false, null, null, null)) {
        if (!m.isStatic() || !m.isPackage()) {
          continue;
        }
        MethodType type = m.getMethodType();
        if (type.equals(INVOKER_METHOD_TYPE) &&
            m.getName().startsWith("invoke_")) {
          String sig = m.getName().substring("invoke_".length());
          int arity = LambdaForm.signatureArity(sig);
          MethodType srcType = MethodType.genericMethodType(arity);
          if (LambdaForm.signatureReturn(sig) == V_TYPE) {
            srcType = srcType.changeReturnType(void.class);
          }
          MethodTypeForm typeForm = srcType.form();
          typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, DirectMethodHandle.make(m));
        }
      }
    }

    // The following are predefined NamedFunction invokers.  The system must build
    // a separate invoker for each distinct signature.

    /**
     * void return type invokers.
     */
    @Hidden
    static Object invoke__V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(0, void.class, mh, a));
      mh.invokeBasic();
      return null;
    }

    @Hidden
    static Object invoke_L_V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(1, void.class, mh, a));
      mh.invokeBasic(a[0]);
      return null;
    }

    @Hidden
    static Object invoke_LL_V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(2, void.class, mh, a));
      mh.invokeBasic(a[0], a[1]);
      return null;
    }

    @Hidden
    static Object invoke_LLL_V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(3, void.class, mh, a));
      mh.invokeBasic(a[0], a[1], a[2]);
      return null;
    }

    @Hidden
    static Object invoke_LLLL_V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(4, void.class, mh, a));
      mh.invokeBasic(a[0], a[1], a[2], a[3]);
      return null;
    }

    @Hidden
    static Object invoke_LLLLL_V(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(5, void.class, mh, a));
      mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
      return null;
    }

    /**
     * Object return type invokers.
     */
    @Hidden
    static Object invoke__L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(0, mh, a));
      return mh.invokeBasic();
    }

    @Hidden
    static Object invoke_L_L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(1, mh, a));
      return mh.invokeBasic(a[0]);
    }

    @Hidden
    static Object invoke_LL_L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(2, mh, a));
      return mh.invokeBasic(a[0], a[1]);
    }

    @Hidden
    static Object invoke_LLL_L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(3, mh, a));
      return mh.invokeBasic(a[0], a[1], a[2]);
    }

    @Hidden
    static Object invoke_LLLL_L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(4, mh, a));
      return mh.invokeBasic(a[0], a[1], a[2], a[3]);
    }

    @Hidden
    static Object invoke_LLLLL_L(MethodHandle mh, Object[] a) throws Throwable {
      assert (arityCheck(5, mh, a));
      return mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
    }

    private static boolean arityCheck(int arity, MethodHandle mh, Object[] a) {
      return arityCheck(arity, Object.class, mh, a);
    }

    private static boolean arityCheck(int arity, Class<?> rtype, MethodHandle mh, Object[] a) {
      assert (a.length == arity)
          : Arrays.asList(a.length, arity);
      assert (mh.type().basicType() == MethodType.genericMethodType(arity).changeReturnType(rtype))
          : Arrays.asList(mh, rtype, arity);
      MemberName member = mh.internalMemberName();
      if (member != null && member.getName().equals("invokeBasic") && member
          .isMethodHandleInvoke()) {
        assert (arity > 0);
        assert (a[0] instanceof MethodHandle);
        MethodHandle mh2 = (MethodHandle) a[0];
        assert (mh2.type().basicType() == MethodType.genericMethodType(arity - 1)
            .changeReturnType(rtype))
            : Arrays.asList(member, mh2, rtype, arity);
      }
      return true;
    }

    static final MethodType INVOKER_METHOD_TYPE =
        MethodType.methodType(Object.class, MethodHandle.class, Object[].class);

    private static MethodHandle computeInvoker(MethodTypeForm typeForm) {
      typeForm = typeForm.basicType().form();  // normalize to basic type
      MethodHandle mh = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
      if (mh != null) {
        return mh;
      }
      MemberName invoker = InvokerBytecodeGenerator
          .generateNamedFunctionInvoker(typeForm);  // this could take a while
      mh = DirectMethodHandle.make(invoker);
      MethodHandle mh2 = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
      if (mh2 != null) {
        return mh2;  // benign race
      }
      if (!mh.type().equals(INVOKER_METHOD_TYPE)) {
        throw newInternalError(mh.debugString());
      }
      return typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, mh);
    }

    @Hidden
    Object invokeWithArguments(Object... arguments) throws Throwable {
      // If we have a cached invoker, call it right away.
      // NOTE: The invoker always returns a reference value.
      if (TRACE_INTERPRETER) {
        return invokeWithArgumentsTracing(arguments);
      }
      assert (checkArgumentTypes(arguments, methodType()));
      return invoker().invokeBasic(resolvedHandle(), arguments);
    }

    @Hidden
    Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {
      Object rval;
      try {
        traceInterpreter("[ call", this, arguments);
        if (invoker == null) {
          traceInterpreter("| getInvoker", this);
          invoker();
        }
        if (resolvedHandle == null) {
          traceInterpreter("| resolve", this);
          resolvedHandle();
        }
        assert (checkArgumentTypes(arguments, methodType()));
        rval = invoker().invokeBasic(resolvedHandle(), arguments);
      } catch (Throwable ex) {
        traceInterpreter("] throw =>", ex);
        throw ex;
      }
      traceInterpreter("] return =>", rval);
      return rval;
    }

    private MethodHandle invoker() {
      if (invoker != null) {
        return invoker;
      }
      // Get an invoker and cache it.
      return invoker = computeInvoker(methodType().form());
    }

    private static boolean checkArgumentTypes(Object[] arguments, MethodType methodType) {
      if (true) {
        return true;  // FIXME
      }
      MethodType dstType = methodType.form().erasedType();
      MethodType srcType = dstType.basicType().wrap();
      Class<?>[] ptypes = new Class<?>[arguments.length];
      for (int i = 0; i < arguments.length; i++) {
        Object arg = arguments[i];
        Class<?> ptype = arg == null ? Object.class : arg.getClass();
        // If the dest. type is a primitive we keep the
        // argument type.
        ptypes[i] = dstType.parameterType(i).isPrimitive() ? ptype : Object.class;
      }
      MethodType argType = MethodType.methodType(srcType.returnType(), ptypes).wrap();
      assert (argType.isConvertibleTo(srcType)) :
          "wrong argument types: cannot convert " + argType + " to " + srcType;
      return true;
    }

    MethodType methodType() {
      if (resolvedHandle != null) {
        return resolvedHandle.type();
      } else
      // only for certain internal LFs during bootstrapping
      {
        return member.getInvocationType();
      }
    }

    MemberName member() {
      assert (assertMemberIsConsistent());
      return member;
    }

    // Called only from assert.
    private boolean assertMemberIsConsistent() {
      if (resolvedHandle instanceof DirectMethodHandle) {
        MemberName m = resolvedHandle.internalMemberName();
        assert (m.equals(member));
      }
      return true;
    }

    Class<?> memberDeclaringClassOrNull() {
      return (member == null) ? null : member.getDeclaringClass();
    }

    BasicType returnType() {
      return basicType(methodType().returnType());
    }

    BasicType parameterType(int n) {
      return basicType(methodType().parameterType(n));
    }

    int arity() {
      return methodType().parameterCount();
    }

    public String toString() {
      if (member == null) {
        return String.valueOf(resolvedHandle);
      }
      return member.getDeclaringClass().getSimpleName() + "." + member.getName();
    }

    public boolean isIdentity() {
      return this.equals(identity(returnType()));
    }

    public boolean isConstantZero() {
      return this.equals(constantZero(returnType()));
    }

    public MethodHandleImpl.Intrinsic intrinsicName() {
      return resolvedHandle == null ? MethodHandleImpl.Intrinsic.NONE
          : resolvedHandle.intrinsicName();
    }
  }

  public static String basicTypeSignature(MethodType type) {
    char[] sig = new char[type.parameterCount() + 2];
    int sigp = 0;
    for (Class<?> pt : type.parameterList()) {
      sig[sigp++] = basicTypeChar(pt);
    }
    sig[sigp++] = '_';
    sig[sigp++] = basicTypeChar(type.returnType());
    assert (sigp == sig.length);
    return String.valueOf(sig);
  }

  public static String shortenSignature(String signature) {
    // Hack to make signatures more readable when they show up in method names.
    final int NO_CHAR = -1, MIN_RUN = 3;
    int c0, c1 = NO_CHAR, c1reps = 0;
    StringBuilder buf = null;
    int len = signature.length();
    if (len < MIN_RUN) {
      return signature;
    }
    for (int i = 0; i <= len; i++) {
      // shift in the next char:
      c0 = c1;
      c1 = (i == len ? NO_CHAR : signature.charAt(i));
      if (c1 == c0) {
        ++c1reps;
        continue;
      }
      // shift in the next count:
      int c0reps = c1reps;
      c1reps = 1;
      // end of a  character run
      if (c0reps < MIN_RUN) {
        if (buf != null) {
          while (--c0reps >= 0) {
            buf.append((char) c0);
          }
        }
        continue;
      }
      // found three or more in a row
      if (buf == null) {
        buf = new StringBuilder().append(signature, 0, i - c0reps);
      }
      buf.append((char) c0).append(c0reps);
    }
    return (buf == null) ? signature : buf.toString();
  }

  static final class Name {

    final BasicType type;
    private short index;
    final NamedFunction function;
    final Object constraint;  // additional type information, if not null
    @Stable
    final Object[] arguments;

    private Name(int index, BasicType type, NamedFunction function, Object[] arguments) {
      this.index = (short) index;
      this.type = type;
      this.function = function;
      this.arguments = arguments;
      this.constraint = null;
      assert (this.index == index);
    }

    private Name(Name that, Object constraint) {
      this.index = that.index;
      this.type = that.type;
      this.function = that.function;
      this.arguments = that.arguments;
      this.constraint = constraint;
      assert (constraint == null || isParam());  // only params have constraints
      assert (constraint == null || constraint instanceof BoundMethodHandle.SpeciesData
          || constraint instanceof Class);
    }

    Name(MethodHandle function, Object... arguments) {
      this(new NamedFunction(function), arguments);
    }

    Name(MethodType functionType, Object... arguments) {
      this(new NamedFunction(functionType), arguments);
      assert (arguments[0] instanceof Name && ((Name) arguments[0]).type == L_TYPE);
    }

    Name(MemberName function, Object... arguments) {
      this(new NamedFunction(function), arguments);
    }

    Name(NamedFunction function, Object... arguments) {
      this(-1, function.returnType(), function,
          arguments = Arrays.copyOf(arguments, arguments.length, Object[].class));
      assert (arguments.length == function.arity()) :
          "arity mismatch: arguments.length=" + arguments.length + " == function.arity()="
              + function.arity() + " in " + debugString();
      for (int i = 0; i < arguments.length; i++) {
        assert (typesMatch(function.parameterType(i), arguments[i])) :
            "types don't match: function.parameterType(" + i + ")=" + function.parameterType(i)
                + ", arguments[" + i + "]=" + arguments[i] + " in " + debugString();
      }
    }

    /**
     * Create a raw parameter of the given type, with an expected index.
     */
    Name(int index, BasicType type) {
      this(index, type, null, null);
    }

    /**
     * Create a raw parameter of the given type.
     */
    Name(BasicType type) {
      this(-1, type);
    }

    BasicType type() {
      return type;
    }

    int index() {
      return index;
    }

    boolean initIndex(int i) {
      if (index != i) {
        if (index != -1) {
          return false;
        }
        index = (short) i;
      }
      return true;
    }

    char typeChar() {
      return type.btChar;
    }

    void resolve() {
      if (function != null) {
        function.resolve();
      }
    }

    Name newIndex(int i) {
      if (initIndex(i)) {
        return this;
      }
      return cloneWithIndex(i);
    }

    Name cloneWithIndex(int i) {
      Object[] newArguments = (arguments == null) ? null : arguments.clone();
      return new Name(i, type, function, newArguments).withConstraint(constraint);
    }

    Name withConstraint(Object constraint) {
      if (constraint == this.constraint) {
        return this;
      }
      return new Name(this, constraint);
    }

    Name replaceName(Name oldName, Name newName) {  // FIXME: use replaceNames uniformly
      if (oldName == newName) {
        return this;
      }
      @SuppressWarnings("LocalVariableHidesMemberVariable")
      Object[] arguments = this.arguments;
      if (arguments == null) {
        return this;
      }
      boolean replaced = false;
      for (int j = 0; j < arguments.length; j++) {
        if (arguments[j] == oldName) {
          if (!replaced) {
            replaced = true;
            arguments = arguments.clone();
          }
          arguments[j] = newName;
        }
      }
      if (!replaced) {
        return this;
      }
      return new Name(function, arguments);
    }

    /**
     * In the arguments of this Name, replace oldNames[i] pairwise by newNames[i].
     * Limit such replacements to {@code start<=i<end}.  Return possibly changed self.
     */
    Name replaceNames(Name[] oldNames, Name[] newNames, int start, int end) {
      if (start >= end) {
        return this;
      }
      @SuppressWarnings("LocalVariableHidesMemberVariable")
      Object[] arguments = this.arguments;
      boolean replaced = false;
      eachArg:
      for (int j = 0; j < arguments.length; j++) {
        if (arguments[j] instanceof Name) {
          Name n = (Name) arguments[j];
          int check = n.index;
          // harmless check to see if the thing is already in newNames:
          if (check >= 0 && check < newNames.length && n == newNames[check]) {
            continue eachArg;
          }
          // n might not have the correct index: n != oldNames[n.index].
          for (int i = start; i < end; i++) {
            if (n == oldNames[i]) {
              if (n == newNames[i]) {
                continue eachArg;
              }
              if (!replaced) {
                replaced = true;
                arguments = arguments.clone();
              }
              arguments[j] = newNames[i];
              continue eachArg;
            }
          }
        }
      }
      if (!replaced) {
        return this;
      }
      return new Name(function, arguments);
    }

    void internArguments() {
      @SuppressWarnings("LocalVariableHidesMemberVariable")
      Object[] arguments = this.arguments;
      for (int j = 0; j < arguments.length; j++) {
        if (arguments[j] instanceof Name) {
          Name n = (Name) arguments[j];
          if (n.isParam() && n.index < INTERNED_ARGUMENT_LIMIT) {
            arguments[j] = internArgument(n);
          }
        }
      }
    }

    boolean isParam() {
      return function == null;
    }

    boolean isConstantZero() {
      return !isParam() && arguments.length == 0 && function.isConstantZero();
    }

    public String toString() {
      return (isParam() ? "a" : "t") + (index >= 0 ? index : System.identityHashCode(this)) + ":"
          + typeChar();
    }

    public String debugString() {
      String s = paramString();
      return (function == null) ? s : s + "=" + exprString();
    }

    public String paramString() {
      String s = toString();
      Object c = constraint;
      if (c == null) {
        return s;
      }
      if (c instanceof Class) {
        c = ((Class<?>) c).getSimpleName();
      }
      return s + "/" + c;
    }

    public String exprString() {
      if (function == null) {
        return toString();
      }
      StringBuilder buf = new StringBuilder(function.toString());
      buf.append("(");
      String cma = "";
      for (Object a : arguments) {
        buf.append(cma);
        cma = ",";
        if (a instanceof Name || a instanceof Integer) {
          buf.append(a);
        } else {
          buf.append("(").append(a).append(")");
        }
      }
      buf.append(")");
      return buf.toString();
    }

    static boolean typesMatch(BasicType parameterType, Object object) {
      if (object instanceof Name) {
        return ((Name) object).type == parameterType;
      }
      switch (parameterType) {
        case I_TYPE:
          return object instanceof Integer;
        case J_TYPE:
          return object instanceof Long;
        case F_TYPE:
          return object instanceof Float;
        case D_TYPE:
          return object instanceof Double;
      }
      assert (parameterType == L_TYPE);
      return true;
    }

    /**
     * Return the index of the last occurrence of n in the argument array.
     * Return -1 if the name is not used.
     */
    int lastUseIndex(Name n) {
      if (arguments == null) {
        return -1;
      }
      for (int i = arguments.length; --i >= 0; ) {
        if (arguments[i] == n) {
          return i;
        }
      }
      return -1;
    }

    /**
     * Return the number of occurrences of n in the argument array.
     * Return 0 if the name is not used.
     */
    int useCount(Name n) {
      if (arguments == null) {
        return 0;
      }
      int count = 0;
      for (int i = arguments.length; --i >= 0; ) {
        if (arguments[i] == n) {
          ++count;
        }
      }
      return count;
    }

    boolean contains(Name n) {
      return this == n || lastUseIndex(n) >= 0;
    }

    public boolean equals(Name that) {
      if (this == that) {
        return true;
      }
      if (isParam())
      // each parameter is a unique atom
      {
        return false;  // this != that
      }
      return
          //this.index == that.index &&
          this.type == that.type &&
              this.function.equals(that.function) &&
              Arrays.equals(this.arguments, that.arguments);
    }

    @Override
    public boolean equals(Object x) {
      return x instanceof Name && equals((Name) x);
    }

    @Override
    public int hashCode() {
      if (isParam()) {
        return index | (type.ordinal() << 8);
      }
      return function.hashCode() ^ Arrays.hashCode(arguments);
    }
  }

  /**
   * Return the index of the last name which contains n as an argument.
   * Return -1 if the name is not used.  Return names.length if it is the return value.
   */
  int lastUseIndex(Name n) {
    int ni = n.index, nmax = names.length;
    assert (names[ni] == n);
    if (result == ni) {
      return nmax;  // live all the way beyond the end
    }
    for (int i = nmax; --i > ni; ) {
      if (names[i].lastUseIndex(n) >= 0) {
        return i;
      }
    }
    return -1;
  }

  /**
   * Return the number of times n is used as an argument or return value.
   */
  int useCount(Name n) {
    int ni = n.index, nmax = names.length;
    int end = lastUseIndex(n);
    if (end < 0) {
      return 0;
    }
    int count = 0;
    if (end == nmax) {
      count++;
      end--;
    }
    int beg = n.index() + 1;
    if (beg < arity) {
      beg = arity;
    }
    for (int i = beg; i <= end; i++) {
      count += names[i].useCount(n);
    }
    return count;
  }

  static Name argument(int which, char type) {
    return argument(which, basicType(type));
  }

  static Name argument(int which, BasicType type) {
    if (which >= INTERNED_ARGUMENT_LIMIT) {
      return new Name(which, type);
    }
    return INTERNED_ARGUMENTS[type.ordinal()][which];
  }

  static Name internArgument(Name n) {
    assert (n.isParam()) : "not param: " + n;
    assert (n.index < INTERNED_ARGUMENT_LIMIT);
    if (n.constraint != null) {
      return n;
    }
    return argument(n.index, n.type);
  }

  static Name[] arguments(int extra, String types) {
    int length = types.length();
    Name[] names = new Name[length + extra];
    for (int i = 0; i < length; i++) {
      names[i] = argument(i, types.charAt(i));
    }
    return names;
  }

  static Name[] arguments(int extra, char... types) {
    int length = types.length;
    Name[] names = new Name[length + extra];
    for (int i = 0; i < length; i++) {
      names[i] = argument(i, types[i]);
    }
    return names;
  }

  static Name[] arguments(int extra, List<Class<?>> types) {
    int length = types.size();
    Name[] names = new Name[length + extra];
    for (int i = 0; i < length; i++) {
      names[i] = argument(i, basicType(types.get(i)));
    }
    return names;
  }

  static Name[] arguments(int extra, Class<?>... types) {
    int length = types.length;
    Name[] names = new Name[length + extra];
    for (int i = 0; i < length; i++) {
      names[i] = argument(i, basicType(types[i]));
    }
    return names;
  }

  static Name[] arguments(int extra, MethodType types) {
    int length = types.parameterCount();
    Name[] names = new Name[length + extra];
    for (int i = 0; i < length; i++) {
      names[i] = argument(i, basicType(types.parameterType(i)));
    }
    return names;
  }

  static final int INTERNED_ARGUMENT_LIMIT = 10;
  private static final Name[][] INTERNED_ARGUMENTS
      = new Name[ARG_TYPE_LIMIT][INTERNED_ARGUMENT_LIMIT];

  static {
    for (BasicType type : BasicType.ARG_TYPES) {
      int ord = type.ordinal();
      for (int i = 0; i < INTERNED_ARGUMENTS[ord].length; i++) {
        INTERNED_ARGUMENTS[ord][i] = new Name(i, type);
      }
    }
  }

  private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();

  static LambdaForm identityForm(BasicType type) {
    return LF_identityForm[type.ordinal()];
  }

  static LambdaForm zeroForm(BasicType type) {
    return LF_zeroForm[type.ordinal()];
  }

  static NamedFunction identity(BasicType type) {
    return NF_identity[type.ordinal()];
  }

  static NamedFunction constantZero(BasicType type) {
    return NF_zero[type.ordinal()];
  }

  private static final LambdaForm[] LF_identityForm = new LambdaForm[TYPE_LIMIT];
  private static final LambdaForm[] LF_zeroForm = new LambdaForm[TYPE_LIMIT];
  private static final NamedFunction[] NF_identity = new NamedFunction[TYPE_LIMIT];
  private static final NamedFunction[] NF_zero = new NamedFunction[TYPE_LIMIT];

  private static void createIdentityForms() {
    for (BasicType type : BasicType.ALL_TYPES) {
      int ord = type.ordinal();
      char btChar = type.basicTypeChar();
      boolean isVoid = (type == V_TYPE);
      Class<?> btClass = type.btClass;
      MethodType zeType = MethodType.methodType(btClass);
      MethodType idType = isVoid ? zeType : zeType.appendParameterTypes(btClass);

      // Look up some symbolic names.  It might not be necessary to have these,
      // but if we need to emit direct references to bytecodes, it helps.
      // Zero is built from a call to an identity function with a constant zero input.
      MemberName idMem = new MemberName(LambdaForm.class, "identity_" + btChar, idType,
          REF_invokeStatic);
      MemberName zeMem = new MemberName(LambdaForm.class, "zero_" + btChar, zeType,
          REF_invokeStatic);
      try {
        zeMem = IMPL_NAMES
            .resolveOrFail(REF_invokeStatic, zeMem, null, NoSuchMethodException.class);
        idMem = IMPL_NAMES
            .resolveOrFail(REF_invokeStatic, idMem, null, NoSuchMethodException.class);
      } catch (IllegalAccessException | NoSuchMethodException ex) {
        throw newInternalError(ex);
      }

      NamedFunction idFun = new NamedFunction(idMem);
      LambdaForm idForm;
      if (isVoid) {
        Name[] idNames = new Name[]{argument(0, L_TYPE)};
        idForm = new LambdaForm(idMem.getName(), 1, idNames, VOID_RESULT);
      } else {
        Name[] idNames = new Name[]{argument(0, L_TYPE), argument(1, type)};
        idForm = new LambdaForm(idMem.getName(), 2, idNames, 1);
      }
      LF_identityForm[ord] = idForm;
      NF_identity[ord] = idFun;

      NamedFunction zeFun = new NamedFunction(zeMem);
      LambdaForm zeForm;
      if (isVoid) {
        zeForm = idForm;
      } else {
        Object zeValue = Wrapper.forBasicType(btChar).zero();
        Name[] zeNames = new Name[]{argument(0, L_TYPE), new Name(idFun, zeValue)};
        zeForm = new LambdaForm(zeMem.getName(), 1, zeNames, 1);
      }
      LF_zeroForm[ord] = zeForm;
      NF_zero[ord] = zeFun;

      assert (idFun.isIdentity());
      assert (zeFun.isConstantZero());
      assert (new Name(zeFun).isConstantZero());
    }

    // Do this in a separate pass, so that SimpleMethodHandle.make can see the tables.
    for (BasicType type : BasicType.ALL_TYPES) {
      int ord = type.ordinal();
      NamedFunction idFun = NF_identity[ord];
      LambdaForm idForm = LF_identityForm[ord];
      MemberName idMem = idFun.member;
      idFun.resolvedHandle = SimpleMethodHandle.make(idMem.getInvocationType(), idForm);

      NamedFunction zeFun = NF_zero[ord];
      LambdaForm zeForm = LF_zeroForm[ord];
      MemberName zeMem = zeFun.member;
      zeFun.resolvedHandle = SimpleMethodHandle.make(zeMem.getInvocationType(), zeForm);

      assert (idFun.isIdentity());
      assert (zeFun.isConstantZero());
      assert (new Name(zeFun).isConstantZero());
    }
  }

  // Avoid appealing to ValueConversions at bootstrap time:
  private static int identity_I(int x) {
    return x;
  }

  private static long identity_J(long x) {
    return x;
  }

  private static float identity_F(float x) {
    return x;
  }

  private static double identity_D(double x) {
    return x;
  }

  private static Object identity_L(Object x) {
    return x;
  }

  private static void identity_V() {
    return;
  }  // same as zeroV, but that's OK

  private static int zero_I() {
    return 0;
  }

  private static long zero_J() {
    return 0;
  }

  private static float zero_F() {
    return 0;
  }

  private static double zero_D() {
    return 0;
  }

  private static Object zero_L() {
    return null;
  }

  private static void zero_V() {
    return;
  }

  /**
   * Internal marker for byte-compiled LambdaForms.
   */
    /*non-public*/
  @Target(ElementType.METHOD)
  @Retention(RetentionPolicy.RUNTIME)
  @interface Compiled {

  }

  /**
   * Internal marker for LambdaForm interpreter frames.
   */
    /*non-public*/
  @Target(ElementType.METHOD)
  @Retention(RetentionPolicy.RUNTIME)
  @interface Hidden {

  }

  private static final HashMap<String, Integer> DEBUG_NAME_COUNTERS;

  static {
    if (debugEnabled()) {
      DEBUG_NAME_COUNTERS = new HashMap<>();
    } else {
      DEBUG_NAME_COUNTERS = null;
    }
  }

  // Put this last, so that previous static inits can run before.
  static {
    createIdentityForms();
    if (USE_PREDEFINED_INTERPRET_METHODS) {
      computeInitialPreparedForms();
    }
    NamedFunction.initializeInvokers();
  }

  // The following hack is necessary in order to suppress TRACE_INTERPRETER
  // during execution of the static initializes of this class.
  // Turning on TRACE_INTERPRETER too early will cause
  // stack overflows and other misbehavior during attempts to trace events
  // that occur during LambdaForm.<clinit>.
  // Therefore, do not move this line higher in this file, and do not remove.
  private static final boolean TRACE_INTERPRETER = MethodHandleStatics.TRACE_INTERPRETER;
}
